Dopant profiling of focused ion beam milled semiconductors using off-axis electron holography; reducing artifacts, extending detection limits and reducing the effects of gallium implantation

Abstract

Focused ion beam (FIB) milling is one of the few specimen preparation techniques that can be used to prepare parallel-sided specimens with nm-scale site specificity for examination using off-axis electron holography in the transmission electron microscope (TEM). However, FIB milling results in the implantation of Ga, the formation of amorphous surface layers and the introduction of defects deep into the specimens. Here we show that these effects can be reduced by lowering the operating voltage of the FIB and by annealing the specimens at low temperature. We also show that the electrically inactive thickness is dependent on both the operating voltage and type of ion used during FIB milling.